Wire bonding apparatus and method

Abstract

A wire bonding apparatus comprises an X-Y table for placing thereon a die pad, on which a rectangular semiconductor chip with a plurality of first bonding pads is mounted, and a package component with a plurality of second bonding pads, a bonding tool for bonding, using a wire, each of the first bonding pads to a corresponding one of the second bonding pads, the bonding tool being movable between a reference position and a bonding level in a Z-direction, a camera system having an auto-focusing function for detecting the Z-directional position of each of the first and second bonding pads, thereby creating Z-directional data concerning the first and second bonding pads, a bonding level computer for calculating bonding levels of the bonding tool on the basis of the Z-directional position data, a bonding sequence computer for determining the motion sequence of the bonding tool on the basis of the calculated bonding levels, and a position/load control selector for selecting, on the basis of the determined motion sequence, a type of control of the bonding tool such that position control is performed while the tool is moved, and load control is performed while the tool performs bonding.

What is claimed is: 
     
       1. A wire bonding apparatus comprising: an X-Y table for placing thereon a die pad, on which a rectangular semiconductor chip with a plurality of first bonding pads is mounted, and a package component with a plurality of second bonding pads, the semiconductor chip being horizontally held above the X-Y table, and the X-Y table being movable in both X- and Y-directions;   a bonding tool for bonding, using a wire, each of the first bonding pads to a corresponding one of the second bonding pads, the bonding tool being movable between a reference position and a bonding level in a Z-direction perpendicular to the X-Y table;   a camera system having an auto-focusing function for detecting the Z-directional position of each of the first and second bonding pads, thereby creating Z-directional data concerning the first and second bonding pads;   a bonding level computer for calculating bonding levels of the bonding tool on the basis of the Z-directional position data concerning the first and second bonding pads;   a bonding sequence computer for determining the motion sequence of the bonding tool on the basis of the calculated bonding levels; and   a position/load control selector for selecting, on the basis of the determined motion sequence, a type of control of the bonding tool such that position control is performed while the tool is moved, and load control is performed while the tool performs bonding.   
     
     
       2. The wire bonding apparatus according to claim 1, wherein the camera system further obtains data concerning the horizontal position of each of the first bonding pads of the horizontally held semiconductor chip, and data concerning the horizontal position of each of the second bonding pads of the package component. 
     
     
       3. The wire bonding apparatus according to claim 2, wherein the bonding sequence computer obtains data concerning the horizontal positions of those two of the first bonding pads which are opposed to each other on a diagonal line, and then corrects prestored position data concerning the first bonding pads, on the basis of the obtained data. 
     
     
       4. The wire bonding apparatus according to claim 3, wherein the bonding sequence computer calculates the horizontal motion sequence of the X-Y table on the basis of the corrected data concerning the first bonding pads. 
     
     
       5. The wire bonding apparatus according to claim 2, wherein the bonding sequence computer obtains data concerning the horizontal positions of those two of the second bonding pads of the package component, which are remotest from each other, and then corrects prestored data concerning the positions of the second bonding pads, on the basis of the obtained data. 
     
     
       6. The wire bonding apparatus according to claim 1, wherein the bonding level computer calculates the distance which the bonding tool covers from the reference position, on the basis of the created data concerning the Z-directional positions of the first and second bonding pads, thereby calculating the bonding level. 
     
     
       7. The wire bonding apparatus according to claim 1, wherein the position/load control selector decelerates a speed of motion of the bonding tool in an initial stage and a final stage of the motion of the tool. 
     
     
       8. The wire bonding apparatus according to claim 1, wherein the position/load control selector outputs, at the time of performing the load control, load data for coupling the wire with the first and second bonding pads by compression bonding. 
     
     
       9. The wire bonding apparatus according to claim 1, further comprising X- and Y-directional motors for moving the X-Y table in the X- and Y-directions, respectively, and X- and Y-driving apparatuses for driving the X- and Y-directional motors, respectively. 
     
     
       10. The wire bonding apparatus according to claim 1, further comprising a Z-directional motor for moving the bonding tool in the Z-direction, and a Z-directional driving apparatus for driving the Z-directional motor. 
     
     
       11. A wire bonding method comprising: the step of placing, on an X-Y table employed in a wire bonding apparatus, a die pad on which a rectangular semiconductor chip with a plurality of first bonding pads is mounted and a package component with a plurality of second bonding pads;   the step of detecting the vertical position of each first bonding pad of the semiconductor chip horizontally held on the die pad by means of a camera with an auto-focusing function, thereby obtaining first vertical position data;   the step of lowering a bonding tool with a bonding wire, to the first bonding pad of the semiconductor chip at a predetermined speed by position control based on the first vertical position data;   the step of switching control from the position control to load control after the bonding tool reaches the first bonding pad, thereby bonding the bonding wire to the first bonding pad;   the step of switching again the control from the load control to the position control to raise the bonding tool;   the step of moving the bonding tool above a corresponding one of the second bonding pads of the package component;   the step of detecting the vertical positions of the second bonding pads by means of the camera with the auto-focusing function, and obtaining second vertical position data;   the step of lowering at the predetermined speed the bonding tool with the bonding wire to the corresponding one of the second bonding pads on the basis of the second vertical position data; and   the step of switching the control from the position control to the load control after the bonding tool reaches the corresponding one of the second bonding pads, thereby bonding the bonding wire to the corresponding one of the second bonding pads.   
     
     
       12. The wire bonding method according to claim 11, wherein the step of lowering the bonding tool at the predetermined speed to the corresponding one of the second bonding pads includes the step of decelerating the predetermined speed in an initial stage and a final stage of a lowering motion. 
     
     
       13. The wire bonding method according to claim 11, wherein the step of lowering the bonding tool at the predetermined speed to each of the first bonding pads includes the step of decelerating the predetermined speed in an initial stage and a final stage of a lowering motion. 
     
     
       14. The wire bonding method according to claim 11, wherein the step of switching the control of the bonding tool to the position control and raising the tool at the predetermined speed includes the step of decelerating the predetermined speed in an initial stage and a final stage of a raising motion. 
     
     
       15. The wire bonding method according to claim 11, wherein the step of obtaining the second vertical position data includes the step of obtaining data concerning the horizontal positions of the second bonding pads of the package component, in addition to the vertical position data. 
     
     
       16. The wire bonding method according to claim 15, wherein the step of obtaining the horizontal position data concerning the second bonding pads includes the step of obtaining data concerning the horizontal positions of those two of the second bonding pads of the package component, which are remotest from each other, thereby correcting prestored data concerning the positions of the second bonding pads. 
     
     
       17. The wire bonding method according to claim 15, wherein the X-Y table covers a desired distance on the basis of the horizontal position data obtained in the step of obtaining the horizontal position data concerning the second bonding pads. 
     
     
       18. The wire bonding method according to claim 11, wherein the step of obtaining the first vertical position data includes the step of obtaining data concerning the horizontal positions of the first bonding pads of the semiconductor chip, in addition to the vertical position data. 
     
     
       19. The wire bonding method according to claim 18, wherein the step of obtaining the horizontal position data concerning the first bonding pads includes the step of obtaining position data concerning those two of the first bonding pads which are opposed to each other on a diagonal line, thereby correcting prestored position data concerning the first bonding pads. 
     
     
       20. The wire bonding method according to claim 18, wherein the X-Y table covers a desired distance on the basis of the horizontal position data obtained in the step of obtaining the horizontal position data concerning the first bonding pads.